Instrument for correcting the line of fire of ordnance



1,615,511 1927' w. F; GROTENDORST INSTRUMENT FOR CORRECTING THE LINE OF FIRE 0F ORDNANCE Original Filed March 29. 1926 Mana er: 224E Grol'ndoraf,

Patented Jan. 25, 1927.

WILLEM FREDERIK GROTENDORST, F HELDER, NETHERLANDS.

INSTRUMENT FOR CORRECTING THE LINE OF FIR-E OF ORDNANCE.

Original application filed March 29, 1926, Serial No. 98,3261, and in Divided. and this application filed August 7, 1926,

This application is a division of my copending application Serial No. 98,32 filed lilarch 29, 1926.

This invention relates to instrun'ients for 5 correcting the line 01? lire of ordnance; its object is to transform observed data into data more suitable for applying the correction.

The invention particularly intended for m use in combination with the apparatus described in the specifications of my co-pend ing applications Ser. No. 98,324 and Ser.

The presentinvention'consists in an im proved instrument for correcting the line of [ire of ordnance, in which a plane table and two transparent plates are pivotally con-- nected together at a common point representing the target, each of these members having a set of parallel lines marked thereon, and said members being adapted to be set so that their parallel lines correspond in direction to the lines joining the target to each of two observation posts and the gun respectively.

The invention is illustrated for the sake of example in the accompanying drawing in which Fig. 1 indicates the general relations existing between the target, the gun, and two observation posts. The spotting stations for observing the splashes at the points of impact may be located in the observation stations, or may be located at other convenient points, and may be on the same side of or on opposite sides of the gun-target line, as desired.

B i way oi illustration, the spotting instruments may be considered as set up in the stations Z, and Z indicated in Fig. 1.. The gun position is indicated at K, and the position oi: a. target at any given time is indicated at I). The distances Z K, Z,Z and Z K, having values a, Z) and a, respectively, can be measured, so that the triangle Z Z K is completely known.

Fig. 2 diagrammatically indicates a constructional form of the improved instrument.

c5 cured to these wires 2 and 3, and on these The spotting board consists of a plane ta-' the Netherlands Hovember 19.

erial No. 127,963.

plates lines are drawn in various colours, and corresponding to successive intervals of for instance, metres each, these lines be ing parallel to the centreline of the plate on which they are marked, that is, the lines are parallel to the wires 2 and 3 respectively. The plane table 1 has marked upon it a fixed line 7 passing through the point 6 and a number of small lines parallel to it and, also corresponding to successive intervals of 50 metres each.

In order to conduct the tiring, the length and direction of the gun-target line KD must be determined, so that the bearings of the lines from the target to the spotting stations and to the gun are known, and the vertical angle 1?, as well as the angle of parallax P, which is the angle subtended at the target between stations Z and the gun K, may be determined simply by subtracting. If the stations Z and Z contain, in addition to the spotting instruments, the observing instrument by which the data is obtained for determining the range. and direction for firing, the values of the angles 6 and P will be determined in computing such range and direction.

The purpose of spotting is to furnish to the gun commander an estimate of the deviation of the splash, in linear units, to the right or left of the gun-target line and over or short oi the target. At the instant of splash, the spotters in spotting stations Z, and Z observe the angle of deviation of the splash from their lines of sight to the target and, knowing the approximate distance of the target from their stations, calculate the lateral deviation in linear units, which they communicate, by telephone or otherwise, to the operators of the spotting board.

The fixed line 7 on the plane table 1 oil Fig. 2 is taken as corresponding with the line 75,1) of Fig. 1 and then the wire 2 set to correspond in direction with the line Z,D. Then those lines on the plane table 1 and on the transparent plate 6 are noted, which correspond with the lateral distance of the shot right or left of the target as observed from Z and Z and their point of intersection is also noted.

Then the wire 3 is set to correspond in direction with the line joining the target and the gun, that is with the line DK of Fig. 1 (the point K representing the gun).

Then the position of the shot relative to the target as Would be observed from the gun is indicated upon the transparent plate 5, and so the lateral displacement right or left can be immediately read from the setof parallel lines on. this transparent plate 5. In many cases the position of the splash over or short of the target is also apparent.

The correct-ions thus found may then be imparted to the battery commander who can then make suitable corrections in the firing data for the next shot.

It will he understood that the number and pacing of the parallel lines depends on the .ize of the instrument, on the degree of accuracy required, and on the maximum range at which the guns are fired. Heavy ordnance therefore requires more lines than medium or light ordnance.

I claim:

1. An instrument for locating the point of impact of projectiles relative to the line of fire, comprising a flat chart and two transparent plates pivotally connected at a common point representing the target, said chart having a line thereon passing through said point and uniformly spaced lines parallel to said line on each side thereof, said plates having arms rigid therewith and extending radially from said pivot point and having thereon uniformly spaced lines parallel to the direction of said arms, said chart having angular graduations thereon.

2. An instrument for locating the point of impact of projectiles relative to the line of fire, comprising a fiat chart and two transparent plates pivotally connected at a common point representing the target, said chart having a line thereon passing through said point and uniformly spaced lines parallel to said line on each side thereof, said plates having arms rigid therewith and extending radially from said pivot point and having thereon uniformly spaced lines parallel. to the direction of said arms, said chart having angular graduations thereon, and the lines on each of said plates and said chart having distinctive characteristics.

In testimony whereof I have signed my name to this specification.

WILLEM FREDERIK GROTENDORST. 

